A Russian plane crashed and another apparently broke up in the air almost simultaneously killing all 89 people aboard the aircraft and raising fears of a double terrorist strike.

Rescuers found wreckage from a Tu-154 jet with at least 46 people on board about nine hours after it issued a distress signal and disappeared from radar screens over the Rostov region 600 miles south of Moscow.

At about the same time, a Tu-134 plane carrying 43 people crashed in the Tula region, south of Moscow.

Emergency officials said there were no survivors from either plane.

Officials made conflicting statements about whether the signal from the Tu-154 indicated a hijacking or other severe problem on the aircraft. There was bad weather overnight in both areas.

The planes had both left Moscow's Domodedovo airport within 40 minutes of each other last night.

President Vladimir Putin ordered an investigation by the nation's main intelligence agency, the Federal Security Service. Its experts were trying to determine whether there were explosions before the crashes, the Interfax news agency said.

There have been fears that separatists in war-ravaged Chechnya could carry out attacks linked to this Sunday's election to replace the region's pro-Moscow president, who was killed by a bombing in May.

Rebels have been blamed for terror strikes that have claimed hundreds of lives in Russia in recent years.

Witnesses said they heard what sounded like three explosions before the first plane crashed. Suspicion of terrorist involvement were compounded when officials said the Sibir airlines Tu-154 that went missing in the Rostov region issued a signal indicating the plane was being seized.